1. Field of the Invention
This invention relates in general to artificial lift systems and, in particular, to an alternate deployment mechanism for artificial lift systems.
2. Brief Description of Related Art
Once an oil and gas well is drilled, producers may rely on subsurface pressure within the fluid reservoir to lift the oil and gas to the surface. The reservoir pressure is sufficient to lift the reservoir fluid the entire distance from the reservoir, through any well deviations, i.e. horizontal sections of the well, to the surface. Where reservoir pressure is insufficient to lift the fluid to the surface, an artificial lift system may be deployed to a location within the well. The artificial lift system typically includes a pump portion and a means to drive the pump to lift the hydrocarbons to the surface. Many well installations use artificial assistance, such as pumps and, in particular, electric submersible pumps (ESPs), to retrieve hydrocarbons and other fluids from subsurface locations. Typically, the pump will be lowered to a subsurface location with the assistance of a drilling or workover rig. For example, the pump may be coupled to an end of a tubing string and then the tubing string may be run into the well installation for deployment of the pump. This process takes a significant amount of time to deploy the pump and retrieve the pump if the pump becomes inoperative. In addition, the cost to rent and operate a drilling or workover rig may be prohibitively expensive for pump retrieval operations.
To overcome some of these problems, tubing strings may be run in place within the well and the pump deployed through the tubing string. A workover or drilling rig may not be needed as the deployment rig may run the pump on a wireline, removing the need of a suitable rig to support the weight of the deploying string. This allows for deployment and retrieval of the pump in shorter time frames, thus reducing the cost associated with both actions. The pump is lowered through the tubing string and landed in an electrical receptacle that receives power from an electric umbilical run with the tubing string. However, these deployment methods may be unable to deploy a pump through a horizontal well section as the methods rely primarily on gravity to move the pump downhole. Wellbore tractors may be coupled to the pump to push or pull the pump through the tubing string. In these embodiments, a workover or drilling rig is not needed as the locomotive means for the pump are placed in hole with the pump. However, these wellbore tractors may face problems when the tractor encounters a deviated portion of the well, or a portion of the well full of debris. In those situations, the wellbore tractor may not be able to move the system through the deviated portion or debris located within the tubing string.
To remove an inoperative pump a well must often be killed. These kill processes may include a kill device placed in the well and a drilling or operational fluid having a heavier specific weight than that of the production fluid that is supplied to the well during workover to remove the rotationally challenged or inoperative pump. Often the heavier fluid permeates into the formation. Once an operational pump is in place within the well, there will be a production lag as the operational fluid that permeated into the reservoir must be removed before production from the well can resume. This lag time may vary in length and represents significant loss of productive operation of the well. Therefore, there is a need for an alternative deployment apparatus that may be conveyed through tubing, that may not be stopped or limited by highly deviated sections of the tubing string or debris located within the tubing string, and that may be deployed in a live well.